1. Technical Field
The present invention relates to a novel recipient or container comprising an outer rigid housing and an inner flexible bag. More particularly, the recipient according to the invention is designed to receive a pressurized propellant gas, such as butane gas.
2. Description of the Related Art
Such a recipient or container is well known. It consists of a rigid outer housing, for example in metal (steel or aluminum) and a flexible inner bag, said bag being fixed to the outer housing and communicating, via a valve, with the outside. Propellant gas, frequently butane gas, is introduced into the space between the inner bag and the rigid housing and exercises pressure on the inner bag. By mechanically operating the valve, the user can empty the bag content through the action of the gas. Such a recipient prevents the content of the bag becoming contaminated with the propellent gas and avoids the gas being discharged into the atmosphere. Such recipients are in current everyday use, for example, for producing shaving foam dispensers and the like.
To perform best, the inner bag needs to be flexible while still remaining strong, so that it can be introduced into the rigid housing immediately after the bag is manufactured. Moreover, the flexible bag must have very low butane permeability, so as to avoid any contamination of the content of the bag and/or any loss of propellant gas pressure. There is thus a need for such bags.
U.S. Pat. No. 3,873,667 discloses such flexible or collapsible bags made from a mixture of polyamide and polyolefin with, optionally, an ionomeric resin. This mixture is subsequently subjected to heat treatment. Thus, according to this prior art, it is necessary to provide an additional treatment step before introducing the flexible bag into the housing which increases the complexity of the process and its cost.
Polyamides, notably PA6, are already known to have great strength properties and show good properties in regard to butane permeability. However, such polyamides are not sufficiently flexible for the resulting bag to be introduced into the rigid housing immediately after manufacture. It has thus been proposed to incorporate plasticizers into the polyamide compositions. The amount of plasticizer needed to reduce the flexural modulus to an acceptable value is, however, very high, being more than 10% by weight. Furthermore, the presence of large amounts of additives, such as plasticizers, in polyamide compositions frequently leads to the emission of harmful products, in particular gaseous emissions, at the high temperatures employed for polyamide composition forming or transformation into bags.
Polyolefins are also considered not suitable for preparing such flexible bags as they have insufficient strength and their butane permeability characteristics are too poor. One way of remedying this problem would be to consider increasing the thickness of the flexible bag. However, significantly increasing the thickness of the bag leads to problems when it is being introduced into the rigid housing and increases production cost.
One therefore desires to find compositions for such flexible bags, designed to be introduced into a rigid housing of the recipient, which:
(a) have low butane permeability; PA1 (b) are transformable without the problem of harmful emissions; PA1 (c) need no supplementary treatment; and PA1 (d) are sufficiently flexible for the bags to be introduced into the rigid housing immediately after they have been manufactured. PA1 (b1) a copolymer of ethylene/alkyl (meth)acrylate/unsaturated monomer having a carboxylic acid function or a carboxylic acid anhydride function, said monomer being grafted or terpolymerized; or PA1 (b2) a copolymer of ethylene/alkyl (meth)acrylate/unsaturated monomer having an epoxy function, said monomer being grafted or terpolymerized. PA1 one or several alpha-omega-amino-acids such as those containing, for example, from 6 to 12 carbon atoms. Examples of such amino acids are aminocaproic, amino-7-heptanoic, amino-11-undecenoic and amino-12-dodecanoic acid; PA1 one or several lactames corresponding to the above amino-acids. Examples of such lactames are caprolactame, oenanlactame and lauryllactame; PA1 one or several substantially stoichiometric combinations of one or several aliphatic and/or cycloaliphatic and/or aromatic-aliphatic diamines, or salts thereof, with one or several aliphatic or aromatic carboxylic diacids or salts thereof. Examples of such diamines are hexamethylenediamine, dodecamethylenediamine, metaxylylenediamine, bis(4-amino-cyclohexyl)methane (hereafter "BACM"), bis(3-methyl-4-amino-cyclohexyl)methane (hereafter "BMACM") and trimethylhexamethylenediamine; examples of diacids are terephthalic, isophthalic, adipic, azelaic, sebacic, suberic and dodecanedicarboxylic acid; PA1 mixtures of the above monomers; and PA1 mixtures of the resulting condensation products, optionally with other polymers compatible with the polyamides. PA1 polyethylene; PA1 PE produced by metallocene and Ziegler-Natta type catalysts; PA1 copolymers of ethylene with alpha-olefins, ethylene representing, for example, from about 35% to about 80% by weight; PA1 ethylene copolymers with one or several comonomers, ethylene representing, for example, from about 35% to about 80% by weight, wherein the comonomers are selected from: (i) carboxylic acid esters; (ii) saturated carboxylic acid vinyl esters such as vinyl acetate; and (iii) unsaturated carboxylic acid esters such as alkyl (meth)acrylate; PA1 mixtures of the above polyethylenes with minor proportions of other polymers, such as elastomers, for example, ethylene propylene rubber (hereafter "EPR"). PA1 polyethylene (HDPE, LDPE, LLDPE or VLDPE) or PE produced by metallocene or Ziegler-Natta catalysts; PA1 ethylene/vinyl acetate copolymers (hereafter "EVA"); PA1 ethylene/methyl or butyl acrylate copolymers.
It has now been found that certain materials, based on polyamide and ethylene copolymer, are suitable for such an end application.